SH3 domains are small, modular domains found in signal transduction molecules and are believed to mediate the formation of protein-protein complexes. We have designed peptide-based, non-natural ligands to the SH3 domain from Sem5. We have the structures of two different ligand-SH3 complexes solved to 2.2 E. However, as the ligands contain unnatural amino acids with unusual sidechains, we would like to obtain better resolution in order to verify sidechain geometries and interactions.